1. Field of the Invention
The present invention generally relates to electron beam recorders and electron beam irradiation position detecting methods and more particularly, to an electron beam recorder and an electron beam irradiation position detecting method, in which signals are spirally recorded on a master of an information rerecording medium such as an optical disc highly accurately.
2. Description of the Prior Art
In general, manufacture an optical disc includes a step in which by using an optical disc master recorder employing a laser or an electron beam as a light source, a master coated with photoresist is exposed and developed such that an optical disc master formed, on its surface, with concave and convex patterns such as information pits and grooves is produced, a step of producing a metallic die which has the concave and convex patterns transferred thereto from the optical disc master and is called a “stamper”, a step of producing a resinous molded substrate by using the stamper and a step in which a recording film, a reflective film, etc. are formed on the molded substrate so as to be bonded to one another.
An electron beam recorder used for exposure at the time an optical disc master is produced by using an electron beam is generally arranged as follows. FIG. 15 shows an arrangement of a conventional electron beam recorder. The conventional electron beam recorder includes an electron beam source 1101 for generating an electron beam 1120 and an electron optical system 1102 which converges the emitted electron beam 1120 onto a resist master 1109 so as to record information patterns on the resist master 1109 in accordance with inputted information signals. The electron beam source 1101 and the electron optical system 1102 are accommodated in a vacuum chamber 1113.
The electron beam source 1101 is constituted by a filament for emitting electrons upon flow of electric current therethrough, an electrode for trapping the emitted electrons, an electrode for extracting and accelerating the electron beam 1120, etc. and is adapted to emit the electrons from one point.
Meanwhile, the electron optical system 1102 includes a lens 1103 for converging the electron beam 1120, an aperture 1104 for determining a beam diameter of the electron beam 1120, electrodes 1105 and 1106 for deflecting the electron beam 1120 in orthogonal directions, respectively in accordance with the inputted information signals, a shielding plate 1107 for shielding the electron beam 1120 bent by the electrode 1105 and a lens 1108 for converging the electron beam 1120 onto a surface of the resist master 1109.
Furthermore, the resist master 1109 is held on a rotary stage 1110 and is moved horizontally together with the rotary stage 1110 by a horizontally traveling stage 1111. If the master 1109 is moved horizontally by the horizontally traveling stage 1111 while being rotated by the rotary stage 1110, the electron beam 1120 can be irradiated spirally on the master 1109 so as to record the information signals of the optical disc spirally on the master 1109.
Moreover, a focusing grid 1112 is provided so as to be substantially flush with the surface of the master 1109. This focusing grid 1112 is provided for adjusting a focal position of the lens 1108 such that the lens 1108 converges the electron beam 1120 onto the surface of the master 1109. If electrons reflected by the focusing grid 1112 or secondary electrons emitted from the focusing grid 1112 upon irradiation of the electron beam 1120 on the focusing grid 1112 are detected by a detector such that a grid image is monitored, the focal position of the lens 1108 can be adjusted from a state in which the grid image is seen.
The electrode 1105 is provided for bending the electron beam 1120 in a direction substantially perpendicular to a feed direction of the horizontally traveling stage 1111. Since the electrode 1105 bends the electron beam 1120 towards the shielding plate 1107 in accordance with signals inputted to the electrode 1105, the electrode 1105 is capable of selecting whether or not the electron beam 1120 is irradiated on the master 1109 such that information pit patterns are recorded on the master 1109.
Meanwhile, the electrode 1106 is provided for bending the electron beam 1120 in a direction substantially perpendicular to that of the electrode 1105, namely, in the substantially same direction as the feed direction of the horizontally traveling stage 1111 and is capable of bending the electron beam 1120 in the substantially same direction as the feed direction of the horizontally traveling stage 1111 in accordance with signals inputted to the electrode 1106. The feed direction of the horizontally traveling stage 1111 corresponds to a radial direction of the master 1109 to be recorded. Variations of a track pitch of the optical disc, etc. can be corrected by the signals inputted to the electrode 1106.
In the optical disc, since the track pitch of information signals to be recorded is required to be recorded highly accurately, feed amount of the horizontally traveling stage 1111, nonrepeatable runout of the rotary stage 1110 or variations of irradiation position of the electron beam 1120 should be controlled with high precision. As disclosed in, for example, Japanese Patent Laid-Open Publication No. 2002-141012, error of the feed amount of the horizontally traveling stage 1110 or the like can be detected by laser measurement, etc. so as to be eliminated by driving the electrode 1106.
In the conventional electron beam recorder, even if mechanical accuracies such as the feed amount of the horizontally traveling stage 1111 and the nonrepeatable runout of the rotary stage 1110 can be corrected, position of the electron beam 1120 itself is quite likely to vary and thus, it is of vital importance to correct variations of the position of the electron beam 1120. The variations of the position of the electron beam 1120 result from great influences such as variations of magnetic field around the recorder, mechanical vibrations, acoustic noise and electrical noise of the recorder, etc. which are exerted on the electron beam 1120.
Generally, since the electron beam source 1101 and the electron optical system 1102 are accommodated in the vacuum chamber 1113, it is quite difficult to detect the variations of the position of the electron beam 1120 accelerated and converged in the vacuum chamber 1113. Meanwhile, a method may be considered in which the electron beam 1120 used for recording is irradiated on a detection object different from the master 1109, for example, the focusing grid 1112 and variations of irradiation position of the electron beam 1120 are detected by using signals of a detector for detecting an image formed on the detection object. However, this method cannot be used when signals are being recorded on the master 1109. Thus, even in this method, it is extremely difficult to detect and correct variations of the position of the electron beam 1120 when the signals are being recorded on the master 1109.